The present invention relates to a ceramic electronic device, such as a multilayer ceramic capacitor, and the production method, and particularly relates to a highly reliable ceramic electronic device having a high withstand voltage and an excellent high temperature load lifetime and the production method.
A multilayer ceramic capacitor is widely used as a highly reliable compact electronic device having a large capacity, and the number to be used in an electric apparatus and an electronic apparatus is also large. In recent years, as apparatuses becoming more compact with higher performance, demands for a multilayer ceramic capacitor to be more compact, larger in capacity, lower in price, and higher in reliability have increasingly become stronger.
A multilayer ceramic capacitor is normally produced by stacking an internal electrode paste and dielectric slurry (paste) by a sheet method or a printing method, etc. and firing the result. As the internal electrodes, Pd and a Pd alloy have been generally used but relatively inexpensive Ni and a Ni alloy have come into use because of a high price of Pd. When forming internal electrodes by Ni or a Ni alloy, there is a disadvantage that the electrodes are oxidized when fired in the air. Therefore, in general, after the binder is removed, dielectric layers are fired by firing under a lower oxygen partial pressure than a balancing oxygen partial pressure of Ni and NiO, then are re-oxidized by annealing.
However, firing in a reducing atmosphere results in a disadvantage that the dielectric layers are reduced and the insulation resistance (IR) becomes low. Therefore, reduction-resistant dielectric materials, which are not reduced even when fired in a reducing atmosphere have been proposed (for example, the Japanese Unexamined Patent Publication No. 9-97734 and the Japanese Unexamined Patent Publication No. 10-74666).
The Japanese Unexamined Patent Publication No. 9-97734 and the Japanese Unexamined Patent Publication No. 10-74666 disclose a dielectric layer having a segregation phase including at least two kinds of oxides of a Li oxide, Si oxide and B oxide. According to these articles, as a result that the dielectric layer includes the segregation phase as above, the moving degree of electrons moving in a grain boundary layer can be lowered and reliability under a high temperature and high voltage can be improved.
However, in the Japanese Unexamined Patent Publication No. 9-97734 and the Japanese Unexamined Patent Publication No. 10-74666, oxides included in the segregation phase were oxides of Li, Si and B, and even if a segregation phase including the oxides is formed, an effect of improving the high temperature load lifetime was insufficient. Furthermore, there was a disadvantage that a temperature characteristic of a capacitance becomes poor and, particularly, a capacity at a high temperature becomes low in these articles.